Modern wireless communications systems and networks depend heavily on airborne (e.g., orbital or aerial) communications platforms to route communications (e.g., transmit and receive information) between ground-based base stations and user terminals. In such a communications environment, sharing spectrum on a non-interfering basis is required for reliable service.
In the wireless communications direction from the user terminals to the orbital or aerial communications platform, a major factor that determines the feasibility of spectrum sharing is the amplitude (or relative gain) of the side lobes of the radio frequency signals transmitted by the antennas of the user terminals.
Conventional solutions to reduce such side lobe interference are generally not suitable for mobile user terminals. As one example, while reflector antennas reduce side lobe interference, they have a large profile and require complex mechanical beam pointing mechanisms to operate in a mobile environment. As another example, while circular planar arrays have a low profile and allow for electronic beam steering, they generate high amplitude side lobes, which limits the spectral efficiency.
Accordingly, those skilled in the art continue with research and development efforts in the field of reducing side lobe interference in a wireless communications system.